This could be done inside an app that could give you the choice to install several such programs.My question is what is the legality of it. Does the fact that wget is used to pull the program in question from the program providers site, mean that the program owner is actually providing the distribution. If so this may be a perfectly legal way to make these programs available.

One thing that could add to this, is including checkinstall. That way the program would be installed as a native slack package, that the user could easily remove at a later date.

Your approach here is similar to that of archlinux's AUR or gentoo portage-repos or *BSD ports repositories. As long as VL does not distribute a binary, VL is excluded from normal "hosting" or "distribution" clauses. Distributing instructions on how to _make_ a binary, is a totally free venue there.